The present invention relates generally to producing printed products with raised printing, and more particularly to digital thermographic methods, systems and products.
Raised print is often desired for such printed products as business cards, invitations, and placards due to the aesthetically pleasing texture and is often equated with high-quality and luxury. Desired haptics effects require a raised print thickness of approximately 50 microns. Traditional raised printing techniques that can achieve this thickness include screen printing and thermography.
Screen printing produces raised print by printing relatively viscous paint at elevated film build through screens/sieves. Thermographic powder can be applied to the wet ink, and the resulting print is first heated to melt the powder and then cooled, resulting in a raised print. Screen printing can yield a film build of greater than 100 microns but present technology requires a photographic pattern in order to transfer the desired structure and is thus limited to non-digital technologies.
Thermography produces raised print by applying thermographic powder to wet ink. The resulting print/powder combination is heated to melt the powder and then cooled to create a solid raised print. Thermography is a well-established raised printing technique that can be used to consistently achieve high quality raised print of desired thicknesses of greater than 100 microns. However, in some applications, such as high-volume printing, thermography may not be ideal. In traditional thermography, the printing press must deliver wet ink in order for the thermographic powder to stick. This can be disadvantageous, as wet sheets delivered by the printing press cannot be stacked prior to processing by the thermographic powder application unit. The desired manufacturing setup is therefore a dedicated printing press whose output directly feeds a thermography press, which receives sheets with wet ink, applies the thermographic powder, shakes or blows off the excess thermographic powder, heats and the cools the sheets. Thus, the full speed capacity of the offset printing press may not be realized as it is limited by the speed of the thermography press.
In addition, the manufacture of a printed product with both flat and raised print is a two-pass process—the first pass to print and dry the flat print followed by a second pass to print the wet ink in areas where thermographic powder is to stick and raised print is to appear. For printed products that include both non-raised print (CMYK) and raised print, the non-raised portion of the printed material is often printed first on a standard CMYK press or printer, and is then introduced to a thermography press to print the raised portions. This arrangement generally limits the paper size to relatively small sheets of paper/substrate due to registration issues. That is, if the flat print and raised print are printed in different machines, the raised print needs to be aligned within a very tight tolerance (e.g., +/−150 micrometers). This is very complicated for the large sheets (B1) that are desirable in mass production. While smaller sheets (e.g., letter- or A4-size sheets) may be used to improve the registration issues, use of smaller sheets may not take full advantage of the printing press capacity and may be unacceptable for the desired production efficiency.
As mentioned above, both screen printing and traditional thermography are non-digital technologies. For digital technologies, Scodix Ltd., headquartered in Rosh Ha'ayin, Israel, produces the Scodix1200™ UV DigitalEmbossing™ press, which produces raised print by printing a clear ink (or glue in combination with foil or coarse pigments for simulated embossed/metallic/glitter special effects) on a CMYK flat-printed sheet and directly curing the ink/glue by UV-irradiation. The Scodix system can achieve a 20-80 micron film build per layer in a 300 dpi resolution.
Another digital system is the Kodak Nexpress s3600, manufactured by Eastman Kodak Company of Rochester, N.Y. The Kodak Nexpress s3600 may include a Fifth Imaging Unit which applies clear dimensional ink during the CMYK printing process to specified areas of the printed product to produce a 3-dimensional appearance. The Nexpress has a single-pass advantage in that CMYK and raised print are produced by a single machine. However, achievable thickness results for the raised output produced by presses of this type using dimensional ink has been found to be in the range of 30 microns.
It would therefore be desirable to find a digital raised print solution that allows the desired raised print thickness achievable by thermography and screen-printing, and which allows printing of both full-color CMYK flat-print areas as well as raised print areas.